Analysing the diets from low-, middle- and high-income countries around the world, a new study spanning 16 years has found a link between consumption of a high number of food made with refined grains and a higher risk of major cardiovascular disease, stroke and death.
According to the Prospective Urban Rural Epidemiology (Pure) study, eating about seven servings per day or at least 350g of refined grain, representing the highest category of intake in the study, was associated with a 27 per cent higher risk of death, 33 per cent higher risk of serious cardiovascular disease and 47 per cent greater risk for stroke, when compared with people who consumed less than 50g per day, which was the lowest category of intake.
The study, which covered 21 countries, including the UAE, primarily evaluated the association between the consumption of three groups of grains – refined grains, whole grains and white rice – with cardiovascular disease, total mortality, blood lipids and blood pressure. The researchers reported no significant adverse health effects related to the consumption of whole grains and white rice.
"Our study from 21 countries showed that higher intake of refined grains was associated with higher risk of total mortality and major cardiovascular events," the researchers said in the study, which was published on The British Medical Journal. "We observed no significant association between intake of whole grains or white rice and clinical outcomes."
As Pure is an observational study, the researchers did not establish any cause for their findings, but with data covering 21 countries across five continents, the results are likely applicable to more people around the world.
The study, which evaluated data from 137,130 people aged 35 to 70 years, offers important insights as cereal grains account for about half of the caloric intake worldwide. Consumption is even higher in low-income and middle-income countries, particularly in Africa and South Asia, where cereal grains contribute about 70 per cent of daily caloric intake.
"Therefore, a detailed examination of the association between the types of cereal grains and health outcomes is warranted," the researchers said.
The researchers examined white rice separately from all other refined grains because more than 60 per cent of the populations involved in the Pure study live in Asia, where rice is a staple food. Intake of white rice was particularly highest in South Asia.
The researchers said a higher intake of white rice was not associated with any of the health outcomes reported with higher consumption of refined grains, although further studies are needed to understand why this is so.
"The reason for the different associations observed with refined grains and white rice is not clear," the researchers said. "However, refined wheat is uniformly and rapidly digested and raises blood glucose, with none of the health advantages of fibre. Varieties of rice such as long grain rice and especially parboiled white rice may have both a definite glycaemic advantage and an overall nutritional advantage over refined wheat products.
"Also, depending on the culture and the nature of the rice eaten, rice may be displacing less-desirable foods."
For the purpose of the study, the researchers defined refined grains as wheat grain products or flours that have been modified to remove the bran and germ and therefore have a low fibre content.
Refined grains are processed at mills to remove the fibrous bran, which makes the grain easier to chew. The germ is also removed as its fat content limits the shelf life of processed wheat products. The resulting refined grain will have a longer shelf life, but is also stripped of valuable nutrients.
"Products in this category are made with refined (white) flour, including white bread, pasta/noodles, breakfast cereals, crackers, and bakery products/desserts containing refined grains," the study said. "For bakery products and desserts, we counted only the proportion of refined grains. Ready-to-eat breakfast made from corn was also included in this group."
The consumption of refined grains was highest in China followed by South East Asia, according to the study. Furthermore, the researchers noted that consumption of refined grains and added sugars has greatly increased over the past few decades.
The benefits of a higher consumption of whole grain, particularly in lowering the risk of mortality and cardiovascular disease, have been studied and advocated by health experts for years, but the Pure researchers noted that the link between refined grains and total mortality and cardiovascular disease has not been clearly defined.
Furthermore, while there have been previous studies conducted on the consumption of carbohydrates, the Pure study offers a more comprehensive examination of diets across multiple regions. "The Pure study has the distinct advantage of examining diets from diverse populations in low-, middle- and high-income countries," the researchers said.
Unlike refined grains, whole grains retain all edible parts of the grain, including the bran, germ, and endosperm, delivering greater nutritional benefits. Whole grains covered in the study included cracked wheat, bulgur, steel cut oats, barley, oat and maize porridges, as well as whole corn and cornmeal. Also included in this category are whole grain flours such as those made from wheat, rye, triticale, oats, barley, maize, finger and pearl millet, sorghum or buckwheat.
The researchers reported a much higher intake of whole grain in Africa compared with the rest of the regions in the study.
What should you eat?
The researchers suggest eating more whole grains and fewer intake of cereal grains and refined wheat products. This means indulging less on food made from refined grains such as croissants and white bread, while including more nutritious options such as brown rice and buckwheat in your diet.
"This study re-affirms previous work indicating a healthy diet includes limiting overly processed and refined foods," said Scott Lear, a co-author of the study and health sciences professor at Simon Fraser University.
In conducting the study, researchers gather information on participants' education, wealth, lifestyle and medical history. Participants were also given validated food questionnaires to assess intakes of refined grains, whole grains and white rice.
Deaths from cardiovascular causes or serious cardiovascular events including heart attack, stroke, and heart failure were then tracked over a period of nine years.
The study was supported by various organisations worldwide, including the UAE’s Sheikh Hamdan Bin Rashid Al Maktoum Award for Medical Sciences and the Dubai Health Authority.